1. Field of the Invention
The present invention relates to a zoom camera of the type in which a photographic zoom lens system and a finder system are independently of each other. More particularly the invention relates to a zoom camera capable of automatically effecting the correction of a parallax in operative association with the extension of a zoom lens.
2. Description of the Prior Art
In the case of a camera in which the optical axis of a phototaking optical system and the optical axis of a finder optical system are spaced apart from each other, as, for example, a compact camera, the occurrence of a parallax or a deviation between the visual field of the phototaking lens and the finder's visual field is inevitable when taking close-ups including, for example, the photographing of a flower at very close range. The occurrence of such parallax causes a phenomenon, as, for example, shown in FIG. 3 in which the image actually taken deviates as indicated by a dotted-line frame with respect to the finder's visual field indicated by a solid-line frame. In the case of a camera incorporating a zoom lens, this parallax appears more eminently with an increase in the image magnification of the phototaking lens system.
Several attempts for correcting such parallax are known. These known methods include, for example, one by which the optical axis of the finder optical system is gradually inclined in mechanically operative association with the extension of the phototaking lens and another by which the visual field frame of the finder is moved mechanically in accordance with the focusing distance.
However, these conventional techniques are disadvantageous in that the whole or part of the finder optical system must be moved mechanically, thus inevitably complicating the internal mechanism of the camera. Therefore, cameras incorporating such parallax correction mechanism are generally expensive.
In order to overcome this deficiency, attempts have been made in which the finder screen is composed of electronic display means such as a liquid crystal display panel and the position and size of an image within the screen are electronically controlled thereby producing the effect of moving the image within the finder's visual field without any mechanical moving mechanism. Even with these method, it is still impossible to avoid an increase in the component parts of the cameras and the mechanism is not suited for use in inexpensive cameras. Also, any attempt to incorporate such parallax correction mechanism in a compact zoom camera requires that the amount of parallax be calculated in accordance with the focusing distance and the focal length and the image on the liquid crystal finder be correspondingly moved by an electronic control, thus making the construction extremely complicated.
In addition, there is another disadvantage that any type of the above-mentioned conventional parallax correction mechanisms has poor adaptability to the automatic focusing mechanisms generally used in the compact cameras. In other words, the conventional parallax correction mechanisms can function only upon the measurement of the distance to an object to be photographed with the result that in order to allow the parallax correction mechanism to function fully satisfactorily, the distance to the object must always be measured so as to continuously correct the parallax in accordance with the resulting information. Where this is not possible, extremely severe restrictions are imposed on the sequence of camara controls so that it is necessary to simultaneously perform the correction of the parallax and the extension of the phototaking lens while preliminarily measuring the distance to the object by half depressing the shutter release bottom. Moreover this series of operations must be completed prior to the operation of shutter release.
Thus, it will be seen that the conventional parallax correction mechanisms and automatic focusing mechanisms have poor adaptability to each other so that, as mentioned previously, in the case of the former mechanical-type mechanisms, there is the undesirable effect of greatly increasing the power consumption of the camera, whereas in the case of the latter electronic-type mechanisms the function becomes such that it is entirely meaningless to the ordinary users who are not skilled in the technique of half-depressing the shutter.